Induction-motor.



PATENTED APR. 14

A. L. CUSHMAN. INDUCTION MOTOR.

APPLICATION FILED 00T.13, 1902.

H0 MODEL.

. CusHMAN UNITED STATES:

PATENT OFFICE.

ABE L. CUSHMAN, OF CONCORD, NEW HAMPSHIRE, ASSIGNOR OFONE-HALF TOBENJAMIN A. KIMBALL, OF CONCORD, NEW HAMPSHIRE.

INDUCTION-MOTOR.

:SPECIFIGATION forming part of Iletters Patent No. 725,225, dated April14, 1903.

Application filed October 13, 1902.

T aZZ whom it may concern:

Beit known that I, ABE L. CUSHMAN, a citizen of the United States,residing at Concord, Merrimack county, New Hampshire, have in- Ventedcertain new and useful Improvements in Induction-Motors, of which thefollowing is a full, clear, and exact description.

My invention relates to inductiommotors, and has for its object tosecure a good starting torque without the insertion or use of any highspecific resistance material in the secondary orinduced circuit. Iaccomplish this end by dividing the winding into a plurality ofsections, all of low specific resistance material, such as copper, andconnecting more or less of these sections in series by means of aswitch, so as to form a closed cir-- cuit. If there are several groups,one section only of each group is used at starting, other sections ofeach group being gradually introduced. This results in smallermagnetization of the armature by the induced currents, and consequentlysmaller reaction at starting, resulting in a good starting torque. Asthe speed increases more sections can be put in in series, increasingthe power without increasing the armature magnetization and reactionuntil the full power of the motor is attained at full speed with all thesections in use.

My invention is illustrated in the accompanying drawings, in whichFigure 1 is a digaram of the windings and a switch. Fig. 2 shows theswitch for connecting the various sections in series. Figs. 3 and atshow other positions of the same switch.

In the drawings, A is a core having slots 1 to 24 of the inducedwinding. In each slot there are three bars I) 0 cl, b 0 61 and b c d ofmaterial of low specific resistance, such as copper, those in everythird slot being connected so as to form three groups of conductors B CD, B C D and B 0 D those bars in the same slot belonging to the samegraup. The ends of each of the three conductors or elements of each setare connected to terminals E E F" F G G the last being connected to thecontact E. The ter- 5o minal F is also connected to a terminal 11 SerialNo. 126,983. (No model.)

opposite to the terminal E. As the switch I, having the insulatedcontact-pieces J and K, is moved it first connects the terminals E Eforming one conductor or element into aclosed circuit. In the nextposition of the switch the terminals E and F are electrically connected,also the terminals E and H, forming a closed circuit of two conductorsor elements arranged in series. In the next position of the switch theterminals E and F are electrically connected and F and G areelectrically connected, forming a closed magnetic circuit of all threeconductors or elements arranged in series, which is the relation inwhich they are arranged when full speed is attained. With the form ofswitch shown in Fig. 2 the movement is longitudinal to the shaft, theconductors B C D being connected to contacts, as shown, and the otherconductors cor- .respondingly arranged and connected.

It will be seen from the above that while only material of low specificresistance is used, yet the energy of the current in the induced portionis kept small at starting without the assistance of any material of lowspecific resistance, and the armature reaction is consequently small andthe starting torque correspondingly large, while when speed has beenacquired the introduction of the other conductors increases the energyin the induced secondary current and increases the power of the motor.

What I claim is- 1. In an induction-motor, the combination of asecondary winding made up of elements of low specific resistance, andmeans for forming a closed induced circuit from a part only of saidelements, and for placing in series with said part additional elements,as desired.

2. In an induction-motor, the combination of a secondary winding made upof elements of low specific resistance, and means for forming a closedcircuit of a greater or less number of said elements arranged in serieswith one another.

3. In an induction-motorythe combination of a secondary winding made upof elements of low specific resistance adapted to be put in series toform a closed magnetic circuit, and a switch, one continuous movement ofwhich increases the number of such elements in longing to the same groupcan be placed in series in said closed circuit While the opposeries toform a closed circuit. site movement decreases such number.

4. In an induction-motor, the combination ABE OUSHMAN' of a plurality ofgroups of elements of 10W Witnesses:

specific resistance and a switch whereby 2 WILLIAM C. BRUNEL, greater'01 less number of the elements be- I HENRY A. KIMBALL.

